Recently, with a growing demand on services using wireless communication systems, there is ongoing active research on a system for ensuring a high data rate in a radio channel. The research on the wireless communication systems focuses on solving problems such as multipath fading, a time varying property of the radio channel, a bandwidth limit, and a power limit of a mobile terminal.
For example, a space-time transmission scheme is one technique for overcoming multipath fading. Orthogonality between received signals needs to be ensured in the use of a space-time transmission scheme. A delay spread of a frequency selective fading channel destroys the orthogonality between the received signals. Therefore, the space-time transmission scheme provides effective performance in a frequency flat block fading channel condition.
In addition, an Orthogonal Frequency Division Multiplexing (OFDM) scheme also shows a characteristic robust to multipath fading. Therefore, space-time OFDM and space-frequency OFDM have been proposed as an effective alternative for overcoming the frequency selective fading. Unlike the space-time OFDM, the space-frequency OFDM can be applied to a fast fading channel in which a channel value does not remain as a constant during at least two transmission blocks.
According to characteristics of the OFDM scheme, one data stream is transmitted through a plurality of subcarriers at a low data rate, thereby generating a high Peak to Average Power Ratio (PAPR). In addition, the OFDM scheme has a problem of performance deterioration due to phase noise and frequency offset. To overcome the problem of the OFDM scheme, a single carrier transmission scheme for performing equalization of a frequency axis has been proposed. The single carrier transmission scheme has a structure and performance similar to those of the OFDM scheme. Advantageously, however, the single carrier transmission scheme is robust to non-linear distortion and subcarrier synchronization distortion, and also has a low PAPR. In addition, when using the single carrier transmission scheme, a transmitter can be implemented in a structure having a significantly low complexity.
To maximize the performance of the single carrier transmission scheme, a system in which the single subcarrier transmission scheme and a Multiple Input Multiple Output (MIMO) scheme are combined is taken into account. Accordingly, there is a need to propose a transmission signal design and a transmitter/receiver structure by which a diversity gain and a multiplex gain can be obtained using the MIMO scheme while maintaining the advantages of the single carrier transmission scheme.